 |
| Titel |
Tropical deep convective life cycle: Cb-anvil cloud microphysics from high-altitude aircraft observations |
| VerfasserIn |
W. Frey, S. Borrmann, F. Fierli, R. Weigel, V. Mitev, R. Matthey, F. Ravegnani, N. M. Sitnikov, A. Ulanovsky, F. Cairo |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 23 ; Nr. 14, no. 23 (2014-12-11), S.13223-13240 |
| Datensatznummer |
250119234
|
| Publikation (Nr.) |
 copernicus.org/acp-14-13223-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
The case study presented here focuses on the life cycle of clouds in the
anvil region of a tropical deep convective system. During the SCOUT-O3
campaign from Darwin, Northern Australia, the Hector storm system has been
probed by the Geophysica high-altitude aircraft. Clouds were observed by in
situ particle probes, a backscatter sonde, and a miniature lidar.
Additionally, aerosol number concentrations have been measured. On 30
November 2005 a double flight took place and Hector was probed throughout its
life cycle in its developing, mature, and dissipating stage. The two flights
were four hours apart and focused on the anvil region of Hector in altitudes
between 10.5 and 18.8 km (i.e. above 350 K potential temperature).
Trajectory calculations, satellite imagery, and ozone measurements have been
used to ensure that the same cloud air masses have been probed in both
flights.
The size distributions derived from the measurements show a change not only
with increasing altitude but also with the evolution of Hector. Clearly
different cloud to aerosol particle ratios as well as varying ice crystal
morphology have been found for the different development stages of Hector,
indicating different freezing mechanisms. The development phase exhibits the
smallest ice particles (up to 300 μm) with a rather uniform
morphology. This is indicative for rapid glaciation during Hector's
development. Sizes of ice crystals are largest in the mature stage (larger
than 1.6 mm) and even exceed those of some continental tropical deep convective
clouds, also in their number concentrations. The backscatter properties and
particle images show a change in ice crystal shape from the developing phase
to rimed and aggregated particles in the mature and dissipating stages; the
specific shape of particles in the developing phase cannot be distinguished
from the measurements. Although optically thin, the clouds in the dissipating
stage have a large vertical extent (roughly 6 km) and persist for at least
6 h. Thus, the anvils of these high-reaching deep convective clouds have
a high potential for affecting the tropical tropopause layer by modifying the
humidity and radiative budget, as well as for providing favourable conditions
for subvisible cirrus formation. The involved processes may also influence
the amount of water vapour that ultimately reaches the stratosphere in the
tropics. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|